I generally add sand to potting soil if I want to increase drainage. In large containers I add a layer of gravel, stones, broken flower pot pieces, or whatever I got in the bottom to help improve drainage.

If you have a large container, besides growing the cilantro why not add some dill, anise, or other annuals with similar habits? I find dill is not only useful, it is a beautiful plant with its feathery fronds and large umbrella-like flowers. All three can be nibbled on fresh or allowed to bolt for seed.

FataMorgana

I don't like vermiculite... with that asbestos association, I just don't feel the need to use it. I think that perlite dust isn't supposed to be good for you either, but I prefer perlite to sand which can compact and be unpleasant in potting soil. But I put perlite in all my potting soils to help with compaction.
I would put another plant in with the cilantro, but I think that dill has different watering needs, liking it dryer? Just don't plant mint with it, it'll crowd out the cilantro. :o)

When I think of your situation with potted Cilantro I wonder why you even concerned about the pot dimentions. We are talking about a plant that reaches cutting height in about 40 days and even though it will regrow after being cut the regrowth will be fernier and more bitter.

When I plant Cilantro I use a pot unsuitable for longer lived herbs and literally pepper the surface with seeds, like wheatgrass, and cover lightly. Two weeks later I find a few more pots and repeat the opperation. The cilantro will grow fine in 1" of potting mix.

Another hint I suggest you might try is to just sow bulk whole corriander seeds from your local supermarket. For $2 you have enough corriander seed to plant more cilantro than you can use in a year. Taste will be the same as the expensive seed, assuming that you only cut it once and then ditch the plant.

I suggest using really BIG, decorative pots, and then mixing several different herbs including some tall ones, as FataMorgana suggested.

The reason is first it will look nice, 2nd, because small pots dry out too fast, and 3rd, because Cilantro aka Coriander (the leaves are usually referred to as "Cilantro" and the seeds, "Coriander", but you will sometimes hear of "Coriander Leaves") being an annual or biennial (short-lived, anyway), will often bolt when its tap root hits the bottom of the pot, or for that matter if it is disturbed. That's probably why it doesn't transplant well. If it bolts you don't get much usable leaf or for that matter seed.

My wife loves it but mine, in the ground, bolted. I think in my climate it might need to be planted in the Fall (well, the seedlings seem to come up NOW left to their own devices) so that it can overwinter as a biennial. As an annual it just didn't get very far.

I've never successfully grown cilantro before and I'm just going off what I read on the internet. This site says you need a 12 inch deep pot - http://culinaryherbguide.com/growingcilantro.htm. I don't know if it's right or not.

I've tried sowing it in small pots before, but the seedlings just keeled over and died before they even put out a set of true leaves. I thought it was the pot size, but on second thoughts maybe it was lack of light. *shrug*

If the 12 inches of soil isn't really necessary, I'll try it in a smallish window-box (approx 6 inches high) instead of the giant bucket. I only want it for the leaves, not the seeds. It's good with fish and Vietnamese noodles. Can I plant it together with some thyme?

I'm a pretty incompetent newbie gardener - heck, I've only just figured out how not to kill potted mint. Though now I seem to have some pest that's eating chunks out of it overnight, and I can't see any bugs in the morning. But that's another story.

I found that thyme (at least for me) resents rich soil. It seems to do better in rather thin, little rich/organic matter soil. I believe cilantro likes a richer soil than thyme.

I would plant other annuals in the same pot rather than perennials like thyme so you can just redo the whole thing when the plants are past the stage you like them in (leaf or seed).

One note on supermarket seed, it may work out well and it may not. It may be seed from a hybrid which may affect the type and growth of the offspring plants. Or there's the possibility the seed may have been treated or something that would impede sprouting. Of course it is cheap and you can always get other seed if it doesn't work out well. I just mention it so you can be aware of possible problems. I have had the best luck in the gardens with a variety (named "Santo") that was intended for seed production. I am able to lightly harvest some leaves as well as getting seed. I found this variety slower to bolt than some others I've tried. It had nice leaf production but I was growing mainly for seed this year. There are other varieties better suited to just leaf use. Any seed company should have those varieties.

FataMorgana

I just planted the cilantro by itself in the big bucket. I'm not too bothered about it looking pretty - are there any practical disadvantages to growing it alone? I used 2 parts potting mix to 1 part perlite and 1 part vermiculite. I would've done 1:1:1 but I ran out. I was surprised by how much water I had to pour into the pot before it started running out the bottom - I had the shower head over it for what felt like a minute. I'm used to tiny little pots. I stuck some wicks in the bottom to aid drainage.

I don't think the supermarkets around here sell cilantro/coriander seeds anyway. Normally I'm all for saving money, but I had to get mine from the garden shop. A packet of them only cost a couple of (US) dollars.

my cilantro bolted and then some of the bottom leaves are turning yellow, red and brown...is the color change because of the bolting?

I grow cilantro in 10-12" containers and they do just fine. Use the leaves and they will go on until the weather gets hot and then they will bolt.

Most annual herbs will do well in 10-12" containers.

I'm a first-timer with plants and chose cilantro as one of them because I love the flavor in my homemade salsa. It bolted and flowered recently and I'm not sure what to do now. Can I save it or do I have to use what I can and let it die? I picked off some of the seeds in case I can use them to start over (if that's the case, I'll need to know what to do for this as well!). I live in an apartment and can only grow in a small container (bummer).

Pot size won't have any effect on seedlings. They say that because they can get rootbound when they are mature. Cilantro bolts if you look at it with a WARM smile. It doesn't last long. Use what you can. They do need a lot of sunlight, though.

Thanks, eahamel. This might sound dumb (I really know next to nothing about gardening), but should I just use what I can off of this plant that has bolted and then throw it away or will it come back eventually?

I grow cilantro in the shade in the summer, and the plants last longer that way and put out more foliage without bolting. If your plants are bolting, chances are they are getting too much sun. For me, cilantro is primarily a winter plant, but I can get it to grow well in the summer if I protect it from the sun. I have it in an 8" pot right now, which seems sufficient.